Vertebral arthrodesis equipment

ABSTRACT

The invention concerns an equipment comprising at least a shoring rod and at least an anchoring assembly ( 1 ) of the shoring rod to a vertebra; each anchoring assembly ( 1 ) comprises a base ( 3 ) integral with a hook ( 2 ), said hook ( 2 ) having a substantially planar part ( 2   b ), extending in a parallel plane, or forming a slight angle, less than 15 degrees, with said base ( 3 ). The invention is characterised in that the base ( 3 ) has a hole ( 10 ) which runs right through it, having an oblong cross-section, and the anchoring assembly comprises a hook-shaped component ( 4 ) whereof the part ( 4   b ) corresponding the base of the hook is linked to a threaded rod ( 5 ), said rod ( 5 ) capable of being engaged in said hole ( 10 ) with the possibility of pivoting about an axis and of displacement in said plane, and capable of receiving s screw ( 6 ).

[0001] The present invention relates to a vertebral arthrodesisequipment.

[0002] Equipment of such kind generally includes two shoring rodsdesigned to be disposed parallel to one another on either side of thevertebrae to be treated, and assemblies for anchoring these rods to thevertebrae, in the form of hooks or pedicle screws. This equipment mayalso include cross-members that approach these rods incrementally, forpreserving their position relative to one another.

[0003] In order to attach a shoring rod to an anchoring assembly, thedesign has provided for the inclusion of two facing walls on theproximal portion of the anchoring assembly, these walls defining aseating for the rod therebetween and furnished with means, such as athreaded or tapping arrangement, for receiving a nut or threaded plugfor locking the rod. These walls impart a “tuning fork” or “tulip” shapeto this proximal portion, such names having now become the accepteddesignations for this type of assembly.

[0004] An existing hook on this type of equipment is designed to beengaged around the pedicle and for this purpose is furnished with acurved vane that is shaped correspondingly. However, the possibilitiesfor implementing this hook are limited to one pedicle support point,which does not allow of adaptation for the various situations that mayarise. In fact, in certain cases depending specifically on the positionand orientation of the shoring rod with respect to this hook ordepending on the quality of the vertebral bone, it may be preferable toselect a different support area.

[0005] In extreme cases, the existing hook may also provoke doubtsregarding the perfect resistance of the assembly that it allows.

[0006] The object of the present invention is primarily to remedy theseessential disadvantages.

[0007] In addition, one significant disadvantage of the existing “tuningfork” (“tulip”) hooks is that occasionally considerable effort isrequired to locate the rods inside the seating for these rods. When thepedicles are small in size, as is the case for thoracic vertebrae,particularly vertebrae D1 to D4, there is a danger that the pedicle maybreak and it is necessary to rely on hooks rather than screws. In viewof the limitations described in the aforegoing, the existing hooks arenot ideally suited for all situations that may arise.

[0008] A further disadvantage of the existing hooks is that their heightis substantial due to the height of the said walls defining the seatingsfor a shoring rod. This height is not particularly inconvenient when thetissues are fairly thick, as is the case at the level of the lumbarvertebrae, but it does create difficulties when tissues becomerelatively thin, as is the case at the level of the thoracic vertebrae,when the equipment may be felt under the skin.

[0009] A further object of the present invention is to remedy thisdisadvantage.

[0010] The equipment to which the invention relates includes in knownmanner at least a shoring rod and at least an anchoring assembly of theshoring rod to a vertebra; each anchoring assembly comprises a baseintegral with a hook and means for attaching said shoring rod to theanchoring assembly; the hook has a curved base part, by means of whichit is attached to the base, and a substantially planar part, extendingin a parallel plane, or forming a slight angle, less than 15 degrees,with said base.

[0011] According to the invention,

[0012] the base has a hole which runs right through it, extending in aparallel direction or forming a slight angle, as described in theaforegoing, with the longitudinal direction of said planar part of thehook; this hole opens towards the hook base in the form of an openinghaving a circular section and, apart from this opening, has an oblongcross-section, the length of which oblong cross-section extending on aparallel plane or forming a slight angle, as described in theaforegoing, with the plane in which said planar part extends; and

[0013] the anchoring assembly comprises a hook-shaped component whereofthe part corresponding to the base of the hook is linked to a threadedrod, said rod capable of being engaged in said hole with the possibilityof pivoting about an axis and of displacement in said plane, and capableof receiving a nut at the end that protrudes through said opening, andwhich nut, when threaded enables the hook formed by the component to bedrawn towards the hook that is integral with the base.

[0014] Each assembly thus includes a first hook, integral with saidbase, and a second hook, engaging with the first hook, which may beplaced in various positions with respect to the first hook, specificallyaccording to a number of pivoting positions about the axis of thethreaded rod and according to a number of positions inclined withrespect to the base, rendered possible by displacement of the rod insaid hole.

[0015] It is possible to clamp two vertebral support zones between thesetwo hooks, of which at least one zone may be chosen to correspond mostclosely to the anchorage to be effected in accordance with the positionor orientation of the shoring rod and/or in accordance with the qualityof the bone. The assembly according to the invention thus particularlyenables pedicular-laminar, laminar-transverse process,pedicular-transverse process or laminar-laminar support areas.

[0016] The means for attaching a shoring rod to an anchorage assembly asdescribed above advantageously include

[0017] a boss integral with the base, defining an interior cavity thatis at least partly spherical in shape, and defining on the outside aportion of a spherical wall; the centres that define the one or morespherical zones of the cavity and said portion of the spherical wall areoffset with respect to each other in a direction perpendicular to thebase;

[0018] a threaded rod including at one end thereof a convex basedesigned to be engaged and retained in said cavity on the base, theconvex base being at least partly spherical in shape, so that itcooperates with the one or more spherical zones of the cavity so as toallow pivoting or articulation of the threaded rod relative to the base

[0019] a stirrup piece having a rounded part suitable for receiving ashoring rod, two superposed wings perforated with holes to allow thestirrup piece to engage with said threaded rod, and a face in the shapeof a portion of hollow sphere, which face being designed to abut saidportion of the spherical wall when the stirrup piece is engaged in saidthreaded rod, and

[0020] a nut that may be screwed onto the threaded rod so as to enablethe stirrup piece to be tightened between the nut and said portion ofthe spherical wall.

[0021] Because of the cavity and the convex base, the threaded rod maybe aligned towards the stirrup piece, which itself has already beenengaged about the shoring rod. This alignment makes it easier for theeyelet on the stirrup piece to be engaged with this threaded rod.

[0022] The nut may then be engaged on the threaded rod and tightened,which has the effect of drawing said concave face of the stirrup pieceinto contact with said portion of the spherical wall of the boss andthen, when such contact is made, and because of the offset between thetwo centres indicated previously, of drawing said threaded rod in adirection substantially perpendicular to the base as the nut istightened further.

[0023] These means of assembly thus facilitate the implantation of theequipment and enable the shoring rod to be positioned progressivelyrelative to the anchoring assemblies that constitute this equipment,which have been positioned on the vertebrae beforehand.

[0024] For purposes of better understanding, the invention is describedagain in the following with reference to the attached schematic drawing,which represents a non-limiting, exemplary preferred embodiment of theequipment under consideration.

[0025]FIG. 1 is a perspective view, before assembly, of an anchoringassembly included therein;

[0026] FIGS. 2 to 4 are end, front and plan views respectively of a baseand a hook included therein, and

[0027]FIG. 5 is an enlarged partial view of a cross-section along lineV-V in FIG. 1 after the anchorage assembly has been attached.

[0028]FIG. 1 represents an anchorage assembly 1 forming part of avertebral arthrodesis equipment.

[0029] This equipment includes two shoring rods, designed to be to bedisposed parallel to one another and on either side of the vertebrae,and anchoring members for anchoring these rods to the vertebrae. Theseanchoring members may be pedicle screws and/or one or more anchoringassemblies 1. The equipment may further include cross-members that aredesigned to draw the shoring rods transversely together progressively,for preserving their position relative to one another.

[0030] These rods, pedicle screws and cross-members are known in and ofthemselves and are therefore not specifically described.

[0031] As is shown in FIG. 1, anchoring assembly 1 comprises a hook 2integral with a parallelepiped base 3, a hook-shaped component 4attached to a threaded rod 5, a screw 6 that may be screwed onto thisthreaded rod 5, a threaded rod 7, a stirrup piece 8, and a nut 9.

[0032] Hook 2 is furnished with a curved base part 2 a, by means ofwhich it is connected to base 3, and an substantially planar part 2 bthat forms an angle of eight degrees with face 3 a of the base to whichhook 2 is attached.

[0033] Base 3 is furnished with a hole 10 which passes completelytherethrough. As is shown more specifically in FIGS. 3 and 4, this hole10 is disposed overall in a direction parallel to face 3 a of the baseand in the longitudinal direction of planar part 2 b. This hole 10 hasopenings in two lateral and opposite faces of base 3.; on the sidefacing base part 2 a, this hole 10 has a circular opening 11 with asection slightly larger than the transverse section of rod 5; apart fromthis opening 11, hole 10 has an oblong cross-section, the length ofwhich oblong cross-section extending parallel to face 3 a.

[0034] Base 3 is also furnished with a boss 15 projecting from the mainface 3 b thereof which is opposite to face 3 a. This boss 15 defines aninterior cavity 16 and on the outside presents a face 17 in the form ofa partly spherical wall.

[0035]FIGS. 3 and 4 show that cavity 16 is defined by two diametricallyopposed zones 20 in the form of a hollow sphere and formed on the sameradius and the same centre, and by two flattened surfaces 21, parallelto the lateral faces of base 3 in which hole 10 does not have anopening.

[0036]FIG. 5 shows that centres C1, C2 that create the one or more zones20 and the portion of the sphere formed by face 17 are offset relativeto each other along a direction perpendicular to said main faces 3 a, 3b of base 3.

[0037] Component 4 includes a part 4 a that is curved in the shape of ahook and a base part 4 b. The base part 4 b is attached to threaded rod5.

[0038] This rod 5 has a diameter such that it may be engaged in hole 10with the possibility of pivoting about its own axis and being displacedin this hole 10.

[0039] On the end that protrudes through hole 11, rod 5 may receive nut6. As it is tightened, this nut thus enables hook 2 to be drawn towardsthe hook formed by part 4 a of component 4.

[0040] Rod 7 is provided at one end thereof with a convex base 25 havingtwo spherical zones and two flattened surfaces to yield a shapecorresponding precisely with zones 20 and flattened surfaces 21. Thisbase is engaged in cavity 16 when assembly 1 is created and then thelateral wall of boss 15 is fastened on this base 25 in such manner as toensure that base 25 is retained in cavity 16, allowing rod 7 to bepivoted relative to base 3, by displacing the spherical zones towardseach other.

[0041] Rod 7 is also furnished with a reduced section 30 that allowssection thereof after the equipment has been finally assembled.

[0042] Stirrup piece 8 includes a rounded part 31 that defines a seatingfor the shoring rod, and two lateral wings 32, in which two holes 33 aresuperposed. These holes 33 enable stirrup piece 8 to be engaged with rod7 so that the shoring rod is attached to assembly 1.

[0043] As is shown in FIG. 5, upper hole 33 is defined by a conical face35, and lower hole 33 is defined partially by a face describing a hollowsphere having the same radius as face 17.

[0044] Assembly 1 thus includes a first hook 2 integral with base 3 anda second hook 4 b, the counterpart of first hook 2, which may be placedin various positions relative to first hook 2, specifically according toa number of pivoting positions about the axis of threaded rod 5 andaccording to a number of positions inclined with respect to base 3,rendered possible by displacement of this rod 5 in hole 10. The assemblyaccording to the invention thus particularly enables pedicular-laminar,laminar-transverse process, pedicular-transverse process orlaminar-laminar support areas.

[0045] Moreover, because of cavity 16 and convex base 25, rod 7 may bealigned with the corresponding stirrup piece 8 at the time the equipmentis placed in position, the stirrup piece itself having already beenengaged about the shoring rod. This alignment makes it easier for theholes 33 to be engaged with this rod 7. Nut 9 may then be engaged on rod7 and tightened, which has the effect of drawing concave face 36 intocontact with face 17 and then, when such contact is made, and because ofthe offset between the two centres C1, C2 indicated previously, ofdrawing rod 7 in a direction substantially perpendicular to base 3 asnut 9 is tightened further.

[0046] These means of assembly thus facilitate the implantation of theequipment and enable the shoring rod to be positioned progressivelyrelative to the one or more anchoring assemblies 1 that constitute thisequipment.

[0047] From the aforegoing, it may be seen that the invention provides avertebral arthrodesis equipment having the significant advantagesdescribed previously with respect to related equipment and the priorart.

[0048] Of course, the invention is not limited to the embodimentdescribed in the preceding text, which served an exemplary purpose only,but on the contrary may be extended to include all the variationscovered in the attached claims.

1. A vertebral arthrodesis equipment including at least a shoring rodand at least an anchoring assembly (1) of the shoring rod to a vertebra;each anchoring assembly (1) comprises a base (3) integral with a hook(2) and means for attaching said shoring rod to the anchoring assembly(1); the hook (2) has a curved base part (2 a), by means of which it isattached to the base (3), and a substantially planar part (2 b)extending in a parallel plane, or forming a slight angle, less than 15degrees, with this base (3) which equipment is characterised in that:the base (3) has a hole (10) which runs right through it, extending in aparallel direction or forming a slight angle as described in theaforegoing, with the longitudinal direction of said planar part (2 b) ofthe hook (2); this hole (10) opens towards the hook base (2) in the formof an opening (11) having a circular section and, apart from thisopening (11) has an oblong cross-section, the length of which oblongcross-section extending on a parallel plane or forming a slight angle,as described in the aforegoing, with the plane in which said planar part(2 b) extends and the anchoring assembly (1) comprises a hook-shapedcomponent (4) whereof the part (4 b) corresponding to the base of thehook is linked to a threaded rod (5), said rod (5) capable of beingengaged in said hole (10) with the possibility of pivoting about an axisand of displacement in said plane, and capable of receiving a nut (6) atthe end that protrudes through said opening (11), and which nut (6),when threaded enables the hook formed by the component (4) to be drawntowards the hook (2) that is integral with the base (3).
 2. Theequipment according to claim 1, characterised in that the means forattaching a shoring rod to an anchoring assembly (1) as describedinclude: a boss (15) integral with the base (3), defining an interiorcavity (16) that is at least partly spherical in shape, and defining onthe outside a portion of a spherical wall (17); the centres (C1, C2)that define the one or more spherical zones (20) of the cavity (16) andthe said portion of the spherical wall (17) are offset, with respect toeach other in a direction perpendicular to the base (3); a threaded rod(7) including at one end thereof a convex base (25) designed to beengaged and retained in said cavity (16) of the base (3), this convexbase (25) being at least partly spherical in shape, so that itcooperates with the one or more spherical zones (20) of the cavity (16)so as to allow pivoting or articulation of the threaded rod (7) relativeto the base (3); a stirrup piece (8) having a rounded part (31) suitablefor receiving a shoring rod, two superposed wings (32) perforated withholes (33) to allow the stirrup piece (8) to engage with said threadedrod (7), and a face (36) in the shape of a portion of hollow sphere,which face (36) being designed to abut said portion of the sphericalwall (17) when the stirrup piece (8) is engaged on said threaded rod(7), and a nut (9) that may be screwed onto the threaded rod (7) so asto enable the stirrup piece (8) to be tightened between the nut and saidportion of the spherical wall (17).
 3. The equipment according to claim2, characterised in that: the cavity (16) is defined by twodiametrically opposed zones (20) in the form of a hollow sphere andformed on the same radius and the same centre, and by two flattenedsurfaces (21), parallel to the lateral faces of base (3) in which hole10 does not have an opening; and in that the said convex base (25) hastwo spherical zones and two flattened surfaces to yield a shapecorresponding precisely with zones (20) and flattened surfaces (21) ofbase (3).
 4. The equipment according to claim 2 or claim 3,characterised in that threaded rod (7) has a reduced section (30) thatallows section thereof after the equipment has been finally assembled.